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Anorectal malformation


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Anorectal malformation

  2. 2. INTRODUCTION • Anorectal malformations constitute one of the commonest congenital anomlies encountered in the newborn. • The enormity of the problem can be judged by the fact that 1 out of every 5000 newborn babies is liable to have this condition. • Male>female (54%:46%) • ARM are currently considered to be “multifactorial”, meaning that there are many unknown factors involved. there are also many genes involved. • Imperforate anus without fistula occurs in 5% of patients, but interestingly, half of them also have Down's syndrome. Patient with Down's syndrome and anorectal malformations have this type of defect 95% of the time.
  3. 3. • The most common defect in females is rectovestibular fistula, whereas the most common defect in males is rectourethral fistula. Cloacal malformations are more common than formerly thought, most likely because they were previously misdiagnosed as rectovaginal fistulas. • Cure in anorectal malformations encompasses anatomical restoration along with functional effectiveness. It is a lifelong misery for a child to have an incontinent opening in the perineum. • It would be better, anytime, to have a permanent colostomy in the anterior abdominal wall where at least a proper colostomy appliance can be fitted.
  5. 5. • The caudal end of hindgut dilates to form the cloaca. The cloaca is connected to the allantois (urachus) ventrally. It is closed caudally by cloacal membrane that represents the opposed layers of ectoderm and endoderm. • The mesoderm at the angle between the allantois and the hindgut proliferates and invaginates the endoderm of the cloaca forming a septum, called urorectal septum. • The septum extends caudally to divide the cloaca into: i. Primitive urogenital sinus ventrally & ii. Anorectal canal dorsally. • Further extension of the urorectal septum caudally divides the cloacal membrane into 2 parts; anterior part called urogenital membrane & posterior part called anal membrane.
  6. 6. • Also, it raises the ectoderm between the previous membranes to form the perineal body. Further proliferation of the mesenchyme around the anal membrane creates an ectodermal depression around it, called proctodeum. • Anorectal canal forms the mucosa of rectum and upper part of anal canal (endodermal in origin). The lower part of anal canal is formed from the proctodeum (ectodermal depression roofed by anal membrane). • The anal membrane ruptures (at the 7th week of development) so that the 2 parts of anal canal become continuous together. Mesenchyme surrounding the anorectal canal forms the musculature of rectum and anal canal.
  7. 7. • Blood supply of anal canal reflects its double origin, as follows: • The upper part of anal canal that is endodermal in origin, being derived from the endoderm of hindgut, is supplied by superior rectal artery which is the continuation of inferior mesenteric artery . • However, the lower part of anal canal that is ectodermal in origin, being derived from the proctodeum (ectodermal depression roofed by anal membrane), is supplied by inferior rectal arteries which are branches of internal pudendal arteries. • The line of fusion of the endodermal and ectodermal parts of anal canal is marked by a line called pectinate line that lies below the anal columns. This line marks the transition of anal canal lining from simple columnar to stratified squamous epithelium.
  9. 9. ANATOMY AND PATHOPHYSIOLOGY • Bowel control implies the ability to detect and retain flatus and stool until the appropriate time for evacuation. • It is the result of a complex interplay among sphincter function, anorectal sensation, and colonic motility. All these factors are affected in children with anorectal malformations. Sphincter Mechanism • The muscle groups of the sphincter mechanism are traditionally described as including the voluntary striated muscles of the external sphincter, the levator musculature and the involuntary, smooth muscle (internal sphincter). • These muscles are innervated by the pudendal nerve,both motor to the external sphincter and sensory to the skin around the anus and derived from the sacral plexus roots S2 to S4, as well as the autonomic nervous system via the nervi erigentes, also derived from segments S2 to S4 of the spinal cord.
  10. 10. • The posterior sagittal approach has demonstrated that the external sphincter runs in a para median direction. • In addition, the muscular boundaries of the external sphincter are fused and thus the components of the external sphincter are indistinguishable. • During posterior sagittal dissection, the junction of the levator musculature with the external sphincter is defined by a vertical group of striated muscle fibers called the muscle complex. • Electrical stimulation of the upper end of the levator group pulls the rectum forward. Stimulation of the muscle complex (vertical fibers) elevates the anus, and stimulation of the para median fibers of the external sphincter closes the anus.
  11. 11. • Children with anorectal malformations have varying degrees of striated muscle development from almost normal-appearing muscle to virtually no muscle at all. • In very high defects, the rectum may rest at the upper part of the funnel-shaped muscle structure, and in lower defects, the rectum may traverse the base of the muscular funnel. • The characteristics and precise limits of the internal sphincter have not been accurately described in normal individuals. • In patients with anorectal malformations , this structure has been a matter of speculation, and few attempts at scientific evaluation have been made.
  12. 12. Sensation and Proprioception • Under normal circumstances, the anal canal is an exquisitely sensitive area. It allows the individual to discriminate solids from liquids and even from gas. The overwhelming majority of children with anorectal malformations are born without an anal canal and therefore cannot discriminate like a normal individual can. • There is, however, another kind of sensation called proprioception. This is described as a vague feeling that is perceived when the rectum is distended, supposedly simultaneous with stretching of the voluntary muscle that surrounds the rectum. • proprioception seems to be present in different degrees in most patients with anorectal malformations. • The clinical implications are obvious. These patients lose control when they suffer an episode of diarrhea. They have the ability to be toilet-trained when they can form solid stool and can learn to perceive it.
  13. 13. Colonic and Rectosigmoid Motility • Normally, it takes between 3 and 6 hours for the gastric contents to transit the small bowel. The intestinal contents reach the cecum in a liquid state. It then takes about 20 to 24 hours for that fecal material to reach the rectum and become formed (solid). • The rectosigmoid acts as a reservoir and keeps the fecal material for a variable time. The anal canal (below the pectinate line) is usually empty because of the action of the surrounding sphincteric mechanism. • Occasionally, however, there are peristaltic waves that push the fecal material toward the anus.
  14. 14. • The rectal contents move distally and touch the exquisitely sensitive tissue of the anal canal, thereby providing the individual with valuable information related to the nature of the rectal contents (gas, solid, liquid). • The distention of the rectum produces a vague sensation of fullness or even colicky pain( proprioception) but does not provide specific information concerning the physical characteristic of the contents. • Very little is known about the mechanism that triggers peristalsis of the rectosigmoid to defecate, but it is clear that the degree of rectal fullness has an important role.
  15. 15. • Thus, when the time comes, the rectosigmoid generates waves of peristalsis aimed at emptying the lumen. • Individuals can restrain this process temporarily by using the voluntary sphincter. With a voluntary decision to allow the stool to come out, the sphincter is relaxed and the individual waits for the next peristaltic wave. • Normal defecation allows massive emptying of the rectosigmoid, followed by another resting period of about 24 hours, during which the rectosigmoid again acts as a reservoir. • The importance of rectosigmoid motility and its relevance for bowel control have largely been underestimated.
  16. 16. • Children subjected to surgical techniques that preserve the rectosigmoid suffer from constipation. Constipation, one of the most important functional sequelae , is probably the result of hypomotility of the rectosigmoid. • The hypomotility is self perpetuating and self-aggravating to the point that if left untreated, megasigmoid develops. In extreme cases, fecal impaction and encopresis or overflow pseudo incontinence may develop. It seems that constipation is worse with lower defects. • Knowing this and the fact that hypomotility can begin a vicious cycle leading to megasigmoid, it is incumbent on the pediatric surgeon to avoid the cycle of hypomotility, constipation, and megasigmoid.
  17. 17. • Aggressive patient follow-up plus dietary, mechanical, and pharmacologic treatment prevents this cycle. • Children with anorectal malformations who, for whatever reason, have lost their rectosigmoid suffer from the exact opposite (i.e., tendency for diarrhea). These children have no reservoir capacity, are highly sensitive to fruits and vegetables, and worst of all, suffer from incontinence.
  19. 19. HISTORY: • Muconuria may be present in rectovesical / rectobulbar fistula. • Abdominal distension and non passage of stool per anus. • Constipation in older patients as solidification of stool occurs by 3-4 months age. GENERAL EXAMINATION OF NEONATE: • Examination of spine • Passage of rigid nasogastric tube • Central cynosis • Limb anomaly • Examination of genitalia
  20. 20. EXAMINATION OF PERINEUM: • Check all orifices.(Anus,vagina,urethra) • meconeum from perineum. • Associated anomalies. BUTTOCK EXAMINATION: • High anomalies -sacrococcygeal agenesis, Flat buttock • Low/intermediate anomalies-Deeply pigmented puckering at the site where normal orifice should have been.
  21. 21. IMAGINE STUDIES • Invertogram • Crosstable lateral radiograph • USG W/A+KUB • USG TRANSPERINEAL • MCU,IVP • CT SCAN ,MRI
  23. 23. Cross table lateral radiograph
  24. 24. CT SCAN: • Mainly required before Definitive surgery. • Clearly shows the anantomy of sphincter muscles. • Delineates the rectal pouch and fistula. • Clearly shows the relationship btw intestine and surrounding muscles. MRI: • Better than CT in soft tissue imagine and no radiation hazard. • Clearly shows whether the pulled through intestine is within levator ani sling or not.
  25. 25. MANAGEMENT • During the first 24 hours, the baby should receive intravenous fluids, antibiotics, and nasogastric decompression to prevent aspiration. • The clinician should use these hours to rule out the presence of associated defects such as vertebral anomalies, cardiac malformations, Tracheoesophageal and/or esophageal atresia, renal anomalies,limb defects.(VACTERL)
  26. 26. POSTERIOR SAGITAL ANORECTOPLASTY • When a low anomaly (perineal fistula) is diagnosed, the surgeon must decide which procedure is appropriate. In the presence of a fistulous track to the perineum, in which the anus is always located anterior to the sphincter mechanism, a limited posterior sagittal anorectoplasty can be performed in the newborn period. • In babies who cannot undergo such a procedure in the newborn period because they are ill and have significant associated anomalies, dilatation of the fistulous tract is appropriate with a plan for repair in the future. • Occasionally, such babies escape detection in the newborn period, and delayed primary repair is then appropriate. • It is advantageous to perform this operation in the first 48 hours of life .
  27. 27. • When such an operation is delayed and performed at several months of life, a complete bowel preparation, including a postoperative period of parenteral nutrition without oral intake, is recommended to avoid a perineal infection. • For a limited posterior sagittal anorectoplasty, the baby is placed prone. In males, a urinary catheter is inserted. The distal end of the rectum is intimately attached to the posterior urethra, and urethral injury must be avoided. • Multiple 6-0 silk sutures are placed at the muco-cutaneous junction around the fistula orifice. An incision divides the posterior sphincter in half and is continued circumferentially around the fistula. • While traction is maintained on the bowel, a circumferential dissection is performed to mobilize the bowel and reposition it within the limits of the external sphincter. Mucosa is sutured to skin with fine, absorbable sutures under slight tension. The perineal body is reconstructed.
  28. 28. COLOSTOMY • Colostomy is usually performed as a first stage in a newborn with a high anomaly. A descending colostomy is a relatively trouble-free stoma. It also leaves the sigmoid colon entirely free for reconstruction. • It is fashioned by making an oblique left lower quadrant incision. The ends of the wound , the proximal part of the stoma is placed at the start of the sigmoid colon , just after the colon comes off its left retroperitoneal attachment. • Stomas placed in mobile portions of the colon are prone to prolapse . The distal part of the stoma, in the upper sigmoid, is made intentionally small in an attempt to prevent prolapse . • The distal segment should be copiously irrigated to remove all meconeum. A colostomy can result in significant morbidity, so it is vital to construct it meticulously.
  29. 29. • Transverse colostomies often lead to prolapse, make cleaning the distal segment difficult, make delineation of the downstream recto-urinary anatomy during the distal augmented-pressure colostogram challenging, and can result in perforation of the colonic segment." Such colostomies also lead to megarectosigmoid and a left microcolon in the defunctionalized segment, particularly when the colostomy is left in place for many months. • A colostomy that is placed too low in the sigmoid can limit pull-through maneuvers. A loop colostomy leads to distal contamination of the urinary stream if there is a fistula and to a dilated megarectosigmoid from stool spillage.
  30. 30. LATER MANAGEMENT AFTER COLOSTOMY • Before reconstruction, the anatomy of the anorectal malformation is delineated by high-pressure distal colostography • In patients who have not already undergone cystourethrography, the necessary information may be gained during the distal colostogram . • Patience is required when performing loopography,with slow distention of the distal rectum. The muscles of the pelvis are normally contracted, and thus the distal rectum is compressed and can at first appear flat at the pubococcygeal line. • With gentle pressure, this flat line begins to bulge, and it is at this point that the examiner can visualize the true extent of the rectum and the presence ofa rectourinary fistula.
  31. 31. ANORECTAL RECONSTRUCTION BASIC PRINCIPLES: • The patient is placed in a prone position with the pelvis elevated. • Special care must be taken to cushion all the pressure areas of the baby's body. Two small bolsters must be used in front of each deltopectoral groove to avoid hyperextension of the neck and shoulders. • A Foley catheter is inserted into the bladder before the patient is positioned. The catheter sometimes goes into the rectum through the fistula rather than into the bladder. • To avoid misplacement, the surgeon can direct the catheter with a lacrimal probe inserted in the tip of the Foley catheter to function as a guide.
  32. 32. • A midline incision is created and the sphincteric mechanism is divided exactly in the midline, with equal amounts of muscle left on each side. • The rationale for this approach is based on the fact that important nerves or vessels do not cross the midline. Everything seems to be terminal in the midline, and there is even a midline raphe that helps the surgeon know that the opening is exactly in the midline. • The retractors should be placed superficially to avoid pressure damage to the nerves that run close to the wound.
  33. 33. PSARP FOR ANOMALIES IN MALE RECTOURETHRAL FISTULA • The incision usually extends from the lower portion of the sacrum through the center of the anal dimple; it is sometimes extended to the perineal body, particularly in boys with a rectum-urethral bulbar fistula. • The levator muscle is located deeper to the ischiorectal fat. This muscle is also divided in the midline. • In boys with a rectum-urethral bulbar fistula, the bowel is very evident and prominent and extends toward the lower part of the incision. In boys with a recto-prostatic fistula, the rectum is much smaller and located much higher in the incision.
  34. 34. • The distal colostogram provides information that is valuable at this point for determining where the location of the rectum can be expected. In the case of a rectum bladder neck fistula, the rectum is not visible through a posterior sagittal approach and should not be searched for. • Temporary silk sutures are placed in the posterior rectal wall for traction, and the rectum is opened exactly in the midline. • Multiple 6-0 sutures are placed Above the fistula in a semicircular fashion. • Once the rectum is fully separated from the urinary tract , circumferencial perirectal dissection is performed to gain enough rectal length to reach perineum.
  35. 35. • The vessels that hold the rectum are coagulated and divided until enough rectal length has been achieved. The urethral fistula is closed using interrupted absorbable sutures. • The perineal body is reconstructed by bringing together the anterior limits of the external sphincter. The posterior edge of muscle complex must be sutures together in the midline. • Anoplasty is performed by placing the rectum within the limits of the external sphincter with the use of interrupted long-term absorbable sutures.
  36. 36. RECTUM BLADDER NECK FISTULA: • In a patient with a rectum bladder neck fistula, an abdominal approach Via either laparoscopy or laparotomy in addition to the posterior sagittal approach, is necessary to mobilize the rectum. IMPERFORATED ANUS WITHOUT FISTULA: • In this patient the blind end of rectum is located at the same level as in a patient with bulbar urethral fistula. The repair is performed as described for recto- urethral fistula.
  37. 37. RECTAL ATRESIA AND STENOSIS • Repair of rectal atresia and stenosis is straightforward. The goal of this procedure is to connect the blind dilated end of the rectum proximally with the anal canal distally. • Both structures are usually separated by a few millimeters of fibrous tissue. The rectum must be sufficiently mobilized to allow the performance of an end-to-end anastomosis to the anal canal. • The wound is then closed by reconstructing all the muscle structures, as previously described.
  38. 38. PSARP FOR ANOMALIES IN FEMALE VESTIBULAR FISTULA • The complexity of this defect is frequently underestimated. Patients with a vestibular fistula are born with the potential for bowel control. Thus, every effort should be made to give these patients the best opportunity to undergo successful reconstruction with a single operation. • With the patient in the prone position, a midline incision is performed, but it is not usually necessary to extend the incision as high as the middle portion ofthe sacrum Which continues around the fistula into the vestibule; multiple 5-0 sutures are placed circumferentially at the fistula site.
  39. 39. • While traction is placed on these sutures, the rectum is dissected in a circumferential manner. The posterior rectal wall can easily be identified, and the dissection must start from the posterior aspect and be extended laterally. • The last step, separation of the rectum from the vagina, is the most delicate part of the dissection. The common wall between the rectum and vagina in this kind ofdefect is long and extremely thin. • The limits of the sphincteric mechanism are electrically determined and marked with temporary silk sutures.
  40. 40. • The perineal body is then reconstructed by bringing together the anterior limit of the external sphincter. • The anterior edge of the muscle complex is reapproximated as described previously for males. The levator muscle is not usually exposed and thus does not need to be reconstructed. • The muscle complex must, however, be reconstructed posterior to the rectum by taking bites of the posterior rectal wall. The anoplasty and wound closure are performed as described for males.
  41. 41. PERSISTENT CLOACA • This female malformation is managed by a variation of posterior sagittal anorectoplasty. It is considered separately because of its complexity. • Repair of this defect has three main goals: achievement of bowel control, urinary control, and sexual function. • A long mid sagittal incision is made that extends from the middle portion of the sacrum through the external sphincter and down into the single perineal opening. • There are two well characterized groups of patients with a cloaca. These two groups represent different technical challenges and must be recognized preoperatively.
  42. 42. • The first consists of patients with a common channel shorter than 3 cm. Fortunately, this group represents the majority of those with cloacas . These patients can usually be repaired via a posterior sagittal approach alone, without laparotomy. • The second group consist of patients with longer common channels. These patients usually need laparotomy.
  43. 43. VAGINAL SWITCH • A specific group of people are born with hydrocolpos and two hemivaginas .The hemivaginas are very large and the two hemiuteri are separated,and the distance between them being longer than the Vertical length of both hemivaginas. In this case it’s wise to perform a maneuver called “vaginal switch”. • The vaginal septum is resected and single vagina is created. Then what is used to be the dome of hemivaginas, where the hemiuterus was resected is turned down to the perineum.
  44. 44. GENERAL PRINCIPLES OF POSTOPERATIVE CARE • In the absence of laparotomy oral feeding may begin in a matter of hours. • Antibiotics are given for 48 hours. • In male who had a rectourethral fistula, the urinary catheter should be left in place for 7 days and in case of female with cloaca repair it is kept for 3 weeks. • If a laparotomy was required for the repair, a suprapubic cystotomy or vesicotomy is created. • A dilatation program is begun 2 wks after surgery twice a day. Every week the size of dilator is increased by 1 unit until the desired size is reached.
  45. 45. • Once the correct size is reached, the colostomy is closed. • Dilatation must continue after closure. Once the dilator can be inserted easily, the schedule is reduced to once a day for 1month, once a week for 1 month, and then once a week for 3 months. • A patient who has 1-3 bowel movements, and shows evidence of a feeling of pushing during bowel movements has a good bowel movement pattern and generally has a good prognosis.
  46. 46. Complications • Constipation(m/c) • Wound infection and retraction • Rectal or vaginal strictures • Rectal mucosal prolapse
  47. 47. CONTINENCE • With the rational administration of bowel irrigation, diet, and drugs, most patients, including those with severe fecal incontinence, are able to remain clean for 24 hours. • Only patients with severe diarrhea secondary to an absent or a short colon have been candidates for a permanent colostomy. • Patients suffer from fecal incontinence are evaluated and classified into those with constipation and those with increased motility(tendency to have diarrhea).
  48. 48. • In the first group, bowel irrigation must be aggressive. A rubber tube is usually introduced high into the sigmoid to clean the bowel. This program takes advantage of the decreased bowel motility in constipated patients: they remain clean for the next 24 hours. No laxatives or diets are given as part of this protocol. • The second group(patients who suffer from increased bowel motility because of loss of the rectal reservoir) require a constipating diet, medication to decrease bowel motility, and a program of colonic irrigation.
  49. 49. • The treatment is adjusted by trial and error over period of week, with 95% of patients remaining clean and having an acceptable social life. • However ,when the patient reaches at the age of 7-12 years more independence is generally needed. • At that point, creation of a continent appendicostomy (Malone procedure) is recommended. • This operation creates a communication between the abdominal wall and the cecum through the appendix of the patient the valve mechanism created allows catheterization the cecum but prevents leakage of stool. Patients are able to administer their own enema while sitting on the toilet.
  50. 50. • The operation consists of plicating the cecum around the native of appendix of the patient and exteriorizing the appendix in the deepest part of the umbilicus to make inconspicuous. • A significant number of patients do have an appendix. • In such cases we make an appendix with a tubularized flap of he cecum and then plicate the cecum around it. • The stoma is also exteriorized through the umbilicus.
  51. 51. • Certain patients in whom the rectum was mislocated during the operation may be candidates for reoperation. This is recommended in patients who were born with a good sacrum , good sphincters, and a malformation with a good prognosis. The results of this procedure vary, with continence achieved in 15% to 46% of patients. • Urologic problems in male patients and female patients without cloacas are rare. In patients with a cloaca 28% with a common channel shorter than 3 cm require intermittent catheterization or a continent diversion to empty their bladder. Patients with common channels longer than 3 cm require intermittent cathetersation.